Multicylinder hot gas engine with power control



y H9? R. R. TOEPEL 3,538,706

MULTICYLINDER HOT GAS ENGINE WITH POWER CONTROL Filed Aug. 2, 1968 2Sheets-Sheet 1 fizz/1611 32 590296! ATTORNEY R. R. TOEPEL Nov. 10, 1970MULTICYLINDER HOT GAS ENGINE WITH POWER CONTROL 2 Sheets-Sheet 2 FiledAug. 2, 1968 HORSEPOWER EFFICIENCY 4O 8O 90 I00 VOLUME PHASE ANGLE luz'chargz' kel United States Patent 3,538,706 MULTICYLINDER HOT GASENGINE WITH POWER CONTROL Richard R. Toepel, Warren, Mich., assignor toGeneral Motors Corporation, Detroit, Mich., a corporation of DelawareFiled Aug. 2, 1968, Ser. No. 749,768 Int. Cl. F03g 7/08; F04d 15/00 US.Cl. 6024 7 Claims ABSTRACT OF THE DISCLOSURE FIELD OF THE INVENTION Myinvention relates to hot gas engines and more particularly to means forcontrolling the power output in certain multicylinder engines of the hotgas type.

DESCRIPTION OF THE PRIOR ART It is known in the art relating to certaintypes of hot gas engines to vary the power output by adjusting the phaserelationships of the pistons which act upon the working gas so as tocarry out a thermodynamic work producing cycle. Such an arrangement is,for example, shown in US. Pat. No. 2,465,139 Van Weenen et al. asapplied to a single cylinder engine having a power piston which variesthe volume of the working space and a displacer piston which moves thegas between the cold and hot zones of the working space.

It is obvious that such phase changing arrangements could be applied tomulti-cylinder engines of the type shown in the aforementioned patentmerely by changing the phase relationships of all the similar pistons inthe same manner. There are, however, other multicylinder engineconstructions, for example, those disclosed in the various figures ofU8. Pat. No. 2,480,525 Van Weenen to which such phase changing conceptsare not obviously applicable. In these latter engines, there is nosingle displacer piston, but two pistons acting together serve the dualfunctions of controlling the volume of the working space andtransferring the working gas back and forth between the hot and coldzones or chambers.

Further, in most of these designs, a single piston is made to act uponthe working gas in two separate working spaces giving what is known as adouble acting piston or a double acting engine arrangement. In thesedouble acting arrangements, each cylinder is interconnected with twoothers so that it is impossible to adjust the phase relationships of allthe working cycles in the same manner. This results from the fact thatmovement of one piston to bring it more in phase with a second pistonwith which it acts to define one working space will move the firstpiston further out of phase with a third piston with which it acts todefine a second working space.

SUMMARY OF THE INVENTION The present invention provides arrangements bywhich the power output of a hot gas engine having one or more doubleacting piston may be controlled by varying the phase relationships ofthe engine pistons. While the in- 3,538,706 Patented Nov. 10, 1970 icevention is broadly applicable to many types of engines in which twopistons acting together control the volume of each working space, anengine arrangement is proposed which is especially suitable for use withthe fundamental inventive concepts.

The basis for the present invention was the discovery, proven bytheoretical studies, that the horsepower and efiiciency curves for a hotgas engine follow relatively uniform patterns from their maximum to zeroas the phase angle between the hot and cold chambers of the Workingspaces is adjusted in either direction from one-quarter cycle degrees)out of phase to either an in phase condition or to a one-half cycledegrees) out of phase condition. This was found to be true even thoughthe pressure and volume conditions differ when moving in the twoopposite directions and this discovery led to the realization thatadjusting the phase of one piston of a multicylinder double actingengine away from the conventional one-quarter cycle out of phaserelationship between the pistons of its connecting cylinders would actto reduce the power output in both its connected working spaces in aboutthe same degree.

The present invention, therefore, makes use of this phenomenon byproviding drive means which permit adjusting the phase relationships ofalternate pistons of the interconnected cylinders of a double actingengine so as to control the power output. As a preferred embodiment, afour-cylinder axial piston arrangement utilizing dual swash plate driveis proposed for advantageous application of the novel concept.

These and other advantages of the invention will be more apparent fromthe following description of the preferred embodiment taken togetherwith the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side elevational view, partially in cross section, of apreferred embodiment of a hot gas engine formed according to theinvention;

FIG. 2 is a cross-sectional view of the hot gas engine of FIG. 1 takengenerally in the plane indicated by the line 22 of the figure;

FIG. 3 is a diagrammatic view of the hot gas engine of FIGS. 1 and 2showing the interrelationship of the various components making up theengine working spaces and FIG. 4 is a graph indicating the curves ofhorsepower and efficiency at various phase angles between the volurnesof the hot and cold chambers of a working space.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the figures ofthe drawings in detail, numeral 10 generally indicates a four-cylinderaxial piston hot gas engine having a drive housing 12 to which areattached four seal retainers 14 secured by collars 16 to four cylindermembers 18, 20. 22 and 24 annularly arranged on parallel axes. Thecylinders terminate in closed ends 26 and may include liners 28 in whichare reciprocably disposed four pistons 30, 32, 34 and 36. The pisto'nscarry suitable seal rings 38 and are connected by rods 40 to followermembers 42 and 43 which reciprocate in sleeves 44 provided in thehousing 12. Rolling seals 46 are provided between the seal retainers 14and rods 40 to prevent the escape of working gas from the cylinders intothe drive housing.

Within the drive housing are a pair of swash plates 48 and 50 carriedfor rotation on concentric shaft members 52 and 54 respectively. Swashplate 48 is connected to a first group of two pistons 32 and 36 bysliding engagement with pivotable bearing members 56 which and seated onthe sides of slots 58 of the follower members 43 connecting with thesepistons. Swash plate 50 connects to a second group of two pistons 30 and34 in a similar manner through their respective bearing members 56 andfollower members 42. Additional elongated slots 60 are provided infollower members 42 and 43 to provide clearance for the rotation of theswash plates 48 and 50 within the follower members to which they are notconnected.

Shaft members 52 and 54 extend into a gear box 62 which containssuitable phase changing mechanism for varying the rotative portions ofswash plates 48 and 50. By the phase changer 62, shaft members 52, 54are interconnected with one another and are both connected so as tosupply power to an output shaft 64.

The interiors of the engine cylinders 18, 22 and 24 are separated bytheir respective pistons into hot chambers 66, 68 70 and 72 formed atthe ends 26 of the cylinders and cold chambers 74, 76, 78 and 80 formedat the opposite ends thereof. Annularly disposed intermediate thecylinders are four canister-like members 82 each of which includes asuitable cooler 84 and a regenerator 86. A heater 88, which may be aburner or other suitable heating device, is located outboard of the ends26 of the engine cylinders. A plurality of tubes 90 extend from the ends26 of the cylinders through heater 88 to the regenerator 86 of theadjacent canister. Short connectors 92 con nect the cooler ends of thecanisters with the cold chamber ends of the adjacent cylinders.

Thus, four separate gas containing working spaces A, B, C and D areformed, each made up of the hot and cold chambers of adjacent cylindersconnected through certain heater tubes 90, a regenerator 86 and itsconnecting cooler 84 and one of the short connectors 92. The volume ofeach working space varies as determined by the positions of the twopistons which define it, one of these pistons varying the volume of thehot chamber and the other varying the volum of the cold chamber. Eachdouble acting piston, in turn, defines both a hot and a cold chamberwhich form parts of two separate working spaces.

FIG. 4 shows the calculated effects on horsepower and efficiency ofchanging the volume phase angle of the hot and cold chambers of oneworking space. That these relationships are not completely obvious isapparent from a consideration of the differing results obtained fromchanging the phase angle in opposite directions from the nominal 90degrees.

The normal working cycle includes events of compression, heating,expansion and cooling. The heating and cooling events take place by thetransfer of gas from the cold chamber through the cooler, regeneratorand heater r to the hot chamber and vice versa. Reducing the phase angleof the volume changes of the hot and cold chambers to zero increasesboth compression and expansion but substantially eliminates gas transferbetween the chambers. Increasing the phase angle to 180 degreesincreases gas transfer but eliminates compression and expansion. Whileboth acts reduce power output to zero, the differences in the method ofreduction make surprising the similarity in the shape of the two halvesof the power curves. Possibly even more surprising is the relativelyhigh efficiency indicated for all but the lower power levels.

In normal full output operation of the engine, the four pistons arereciprocated continuously but with adjacent pistons having a 90 degreeor one-quarter cycle phase difference from one another. As shown in FIG.3, the pistons follow one another in the sequence 36, 34, 32,

with one-quarter cycle between them. This results in the cycle of volumechanges of the respective hot chambers leading the volume changes oftheir connected cold chambers by 90 degrees or one-quarter cycle whichgives a positive work outputat a maximum power level for each workingspace. This work output is transferred by the pistons to their connectedswash plates 48, 50 and thence through the phase changer 62 to theoutput shaft 64.

In order to reduce the engine power output, the phase changer 62 isoperated by control means, not shown, so as to rotate either one or bothof the swash plates as described through an angle of up to degrees withrespect to one another. This changes the phase relationships of thevarious pistons.

Thus, for example, the position of piston 36 may be retarded one-quartercycle or 90 degrees which will put this piston in phase with piston 34.At the same time, piston 32 will be moved 90 degrees in a retardingdirection so that it is in phase with piston 30 and degrees or one-halfcycle out of phase with piston 34. Pistons 36 and 30 will also be 180degrees or one-half cycle out of phase with one another. By thisadjustment, the hot and cold chambers of working spaces B and D changefrom 90 degree phase angles to phase angles of zero. This reduces thepower output of these working spaces as shown in the left hand portionof the curve of FIG. 4 from a maximum to zero. At the same time, the hotand cold chambers of working spaces A and C have their phase anglesincreased from 90 degrees to 180 degrees, which reduces the power ofthese working spaces as shown in the right hand side portion of thecurve of FIG. 4 from a maximum to zero. It should be obvious that anyintermediate adjustment of the phase angle will result in anintermediate power output from the engine with approximately equal poweroutputs being obtained from each of the working spaces as indicated bythe uniform shape of both sides of the horsepower curve of FIG. 4.

While the invention has been described by reference to a preferredembodiment chosen for purposes of illustration, it should be apparentthat the concepts involved are equally applicable to other hot gasengines in which double acting cylinder arrangements may be used. Forexample, the phase changing concepts disclosed herein could equally wellbe applied to any of the engines shown in the various figures of thepreviously mentioned US. Pat. No. 2,480,525, the disclosure of which ishereby incorporated herein by reference. Many other modifications of theinvention within the spirit and scope of the inventive conceptspresented should also be obvious to those skilled in the art.

What is claimed is:

1. A hot gas engine adapted to operate with a gaseous working fluid andcomprising a plurality of cylinders,

a plurality of pistons not less than three in said engine cylinders anddefining therewith at least two hot chambers and at least two coldchambers, the volume of each of said chambers being determined by theoperative position of one of said pistons,

passage means connecting each hot chamber detfined by one of saidpistons with a cold chamber defined by another of said pistons to form aplurality of working spaces each having the volume thereof determined bythe operative positions of two pistons,

said pistons being classifiable into first and second groups eachconsisting of one only of the pistons determining the volume of each ofsaid working space, each group defining at least one hot chamber and atleast one cold chamber,

first and second drive means connected with the pistons of said firstand second groups respectively and opperative to maintain predeterminedphase relationships between the pistons of said first group and betweenthe pistons of said second group, said drive means being adapted tomaintain a controlled phase relation between said pistons for operationat maximum engine power such that the volume change of each hot chamberleads the volume change of the cold chamber of its respective workingspace by one-quarter of a cycle,

said second drive means being adjustable with respect to said firstdrive means to reduce engine power by unidirectionally changing thephase relations of the pistons of said second group with respect to thepistons of said first group by an amount up to onequarter of a cycle,said one-quarter cycle change resulting in the volume changes of the hotchambers of certain working spaces being in phase with the volumechanges of the respective cold chambers thereof while the volume changesof the hot chambers of the remaining working spaces are one-half cycleout of phase with the volume changes of the respective cold chambersthereof, each such condition resulting in no power output from thepistons of the various working spaces.

2. The combination of claim 1 wherein said engine has four cylinderseach having one double acting piston therein, two of said pistons beingconnected to said first drive means and two of said pistons beingconnected to said second drive means.

3. The combination of claim 2 wherein said engine cylinders areannularly arranged on parallel axes and said drive means comprise firstand second swash plates.

4. A hot gas engine adapted to operate with a gaseous working fluid andcomprising four cylinders,

a double acting piston in each cylinder and defining therewith a hotchamber at one end and a cold chamber at the other, the volume of eachof said chambers being determined by the operative position of saidpiston,

passage means connecting the hot chamber of each cylinder with the coldchamber of another to form a plurality of working spaces each having thevolume thereof determined by the operative positions of the two pistons,

said pistons being classifiable into first and second groups eachconsisting of two pistons which together determine, in part, the volumeof all of said working spaces,

first and second drive means connected with the pistons of said firstand second groups respectively and operative to maintain an out of phaserelationship between the pistons of said first group and between thepistons of said second group, said drive means being adapted to maintaina one-quarter cycle phase angle between the pistons of said first andsecond groups for operation at maximum engine power such that the volumechange of each hot chamber leads the volume change of the cold chamberof its respective working space by one-quarter of a cycle,

said second drive means being adjustable with respect to said firstdrive means to reduce engine power by unidirectionally changing thephase relations of the pistons of said second group with respect to thepistons of said first group by an amount up to onequarter of a cycle,said change resulting in a decrease in the phase angle between the hotand cold chambers of two of said working spaces and a comparableincrease in the phase angle between the hot and cold chambers of theother two of said working spaces.

5. The combination of claim 4 wherein said engine cylinders areannularly arranged on parallel axes and said working spaces are formedby connection together of adjacent cylinders, said first and secondgroups consisting of oppositely disposed pistons.

6. The combination of claim 5 wherein said drive means comprise firstand second swash plates rotatable on a common axis, and relativelyrotatable to vary the phase relationships of the tfirst and secondgroups of pistons.

7. The method of controlling the power output of a multicylinder hot gasengine having a plurality of pistons and a plurality of working spaceseach including a hot chamber defined in part by one of said pistons in acold chamber defined in part by another of said pistons, said methodcomprising the steps of controlling the phase relations of said pistonsduring reciprocation thereof to obtain a leading phase angle ofone-quarter cycle for the volume variations of the hot chamber of eachworking space over the cold chamber thereof for maximum engine power andreducing engine power by changing the phase relations of the pistons todecrease the leading phase angles of the hot chambers over the coldchambers of certain of the engine working spaces up to a maximumdecrease of one-quarter cycle to an in-phase condition, Whileconcurrently increasing the leading phase angles of the hot chambersover the cold chambers of the remaining engine working spaces in acomparable amount up to a maximum increase of onequarter cycle to aone-half cycle out-of-phase condition.

References Cited UNITED STATES PATENTS 970,640 9/ 1910 McClintock 91175XR 2,445,281 7/1948 Rystrom 91l75 XR 2,468,293 4/1949 Du Pre 24 XR2,480,525 8/1949 Van Weenen 60--24 2,583,311 1/ 1952 Van Heeckerson 60242,611,235 9/1952 Van Weenen 6024 2,664,699 1/1954 Kohler 6024 2,691,35010/1954 Greer 103-37 3,117,414 1/1964 Daniels et al. 6024 3,191,5426/1965 Hughes l0337 XR 3,315,465 4/1967 Wallis 6024 FOREIGN PATENTS336,810 10/1930 Great Britain. 812,83 6 5/ 1959 Great Britain.

MARK M. NEWMAN, Primary Examiner I. PAYNE, Assistant Examiner U.S. Cl.X.R.

